Apollo Bio Filter
If your reg uses standard 1st stage threads order the 3/8 thread version. If your 1st stage hose uses the larger 1/2 inch size (Mares Abyss, US Divers, etc) order the 1/2 size. Then you simple screw it into first stage port and hook up your reg hose. The rubber shock mount will stop unit from getting jarred and the easy to open chamber requires no tools - just your hands.
Just add some water to the sponge and screw it back together and increase the humidity of the air you're breathing to 60% - instead of the .1% you're used to!
Apollo Bio Filter - Accessories-General